Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Added risk approach

Selenium is naturally present in all environmental compartments. The median baseline background concentration in unpolluted stream water in Europe is 0.32 µg Se/L (Vercaigne et al., 2010). These background concentrations are significant compared to the PNEC freshwater (2.67 µg Se/L). Moreover, toxicity due to dietary exposure to Se is more critical compared to direct exposure to dissolved Se, with a critical Se concentration in water for secondary poisoning of 0.21µg Se/L (based on PNECoral of 1 mg Se/kg diet and a generic bioaccumulation factor of 4721 L/kg). Therefore, the added risk approach is employed and all NOEC and EC10 values are based on added selenium concentrations, without taking into account the natural background concentration in water. In essence this added risk assessment approach assumes that species are fully adapted to the natural background concentration and therefore that only the anthropogenic added fraction should be regulated or controlled (Appendix R.7.13-2 of the REACH guidance on “Environmental risk assessment for metals and metal compounds”). Because measured background concentrations in exposure media are generally below the detection limit (generally 1-2 µg Se/L) and chronic NOEC values vary between 10 and 11000 µg Se/L, these NOEC values can be considered as added dissolved Se concentrations.

Summary toxicity data

Reliable ecotoxicity results selected for the effect of selenium on aquatic organisms are available for H2SeO3, Na2SeO3, SeO2 Na2SeO4 and seleno-(D)L-methionine. All data were reported based on dissolved elemental Se concentrations. The data for Se-(D)L-methionine were not taken into account for the assessment of direct effects of selenite to aquatic organisms because there is some concern on different biochemical behaviour of this selenium containing amino acid compared to inorganic Se compounds. The data available for the inorganic Se compounds do not allow conclusions on the effect of water properties (pH, hardness, etc.) or Se substance on toxicity of selenium to aquatic organisms. Therefore, all reliable toxicity data for all inorganic Se substances, expressed on a dissolved selenium basis, were grouped for the effects assessment.

The table below presents an overview of the lowest reliable toxicity data for the various trophic levels of aquatic organisms.

Trophic level Substance Species Parameter Endpoint  Value (µg Se/L)  Reference
 Acute toxicity, freshwater             
 Fish  SeO2 Pimephales promelas  mortality   96-h LC50   2060  Cardwell et al., 1976
 Invertebrates  Na2SeO3 Daphnia magna  mortality   48-h LC50   550  Maier et al., 1993
 Algae  Na2SeO3 Selenastrum capricornutum growth rate  72-h EC50  44240  LISEC, 1992
 Acute toxicity, marine water             
 Fish  Na2SeO3 Morone saxatilis  mortality  96-h LC50  3300  Chapman, 1992
 Algae  Na2SeO4  Dunaliella viridis  growth rate  96-h EC50  45000  Brix et al., 2004
 Chronic toxicity, freshwater            
 Fish  Na2SeO3  Lepomis macrochirus  prespawning mortality  258-d NOEC 10   Hermanutz et al., 1992
 Invertebrates  H2SeO3  Daphnia magna  reproduction  28-d NOEC  70  Kimball, 1978
 Algae  Na2SeO4  Chlamydomonas reinhardtii  growth  96-h NOEC  197  Geoffroy et al., 2007
 Plants  Na2SeO3  Lemna minor  growth (%surface coverage)  14-d NOEC  80  Jenner and Janssen-Mommen, 1993
 Chronic toxicity, marine water        
 Invertebrates  Na2SeO3  Allorchestes compressa  reproduction  28-d NOEC  44  Ahsanullah and Brand, 1985
 Algae  Na2SeO4  Dunaliella viridis  growth rate  72-h NOEC 11000   Brix et al., 2004

Reliable short-term toxicity data for freshwater organisms are available for three trophic levels: aquatic invertebrates, fish and algae. Acute L(E)C50 values vary between 550 and 48200 µg Se/L, with the lowest acute effect value was a 48-h LC50 of for the effect of Na2SeO3 on mortality of Daphnia magna. Acute toxicity data are also available for marine fish and algae (3300-76000 µg Se/L).

Reliable long-term toxicity data are available for 11 freshwater organisms covering the three trophic levels. The lowest chronic NOEC, 10 µg Se/L, was observed for the effect of Na2SeO3 on pre-spawning mortality of Lepomis macrochirus after 238 days exposure. Reliable long-term toxicity data were also identified for the effect of Na2SeO3 and Na2SeO4 on a marine alga and two marine invertebrates with NOEC values between 44 and 11000 µg Se/L.

Data for dietary toxicity are also available for 6 freshwater fish species with NOECoral values between 3.7 and 89.8 mg/kg dw diet for growth and mortality based on studies with Na2SeO3, SeO2, Na2SeO4 and seleno-(D)L-methionine. Because after release in the environment, inorganic Se can be transformed into Se containing amino acids, data for seleno-methionine and seleno-cysteine are included for the assessment of secondary poisoning (through PNECoral and bioconcentration factors).